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https://issues.apache.org/jira/browse/YARN-4053?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15004727#comment-15004727
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Varun Saxena commented on YARN-4053:
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bq. Would it be safe to always assume a long converter?
I think while processing it would be safe to assume with current columns and 
converters. The issue comes if somebody changes the converter corresponding to 
column/column prefix in future. And possibly forgets to change here. Arguably 
though its difficult to miss such a change after testing.

The reason this iterating over all columns/column prefixes was added was to 
handle future column additions or change in converter for existing columns.

Getting the converter on every iteration was a concern even for me. That's why 
I am doing it only when column qualifier changes while iterating cells.
Not sure if we can get hold of all possible column qualifiers(and hence the 
converter) for this scan in the constructor.

Another option would be to use cell tags to identify converters.




> Change the way metric values are stored in HBase Storage
> --------------------------------------------------------
>
>                 Key: YARN-4053
>                 URL: https://issues.apache.org/jira/browse/YARN-4053
>             Project: Hadoop YARN
>          Issue Type: Sub-task
>          Components: timelineserver
>    Affects Versions: YARN-2928
>            Reporter: Varun Saxena
>            Assignee: Varun Saxena
>              Labels: yarn-2928-1st-milestone
>         Attachments: YARN-4053-YARN-2928.01.patch, 
> YARN-4053-YARN-2928.02.patch, YARN-4053-feature-YARN-2928.03.patch
>
>
> Currently HBase implementation uses GenericObjectMapper to convert and store 
> values in backend HBase storage. This converts everything into a string 
> representation(ASCII/UTF-8 encoded byte array).
> While this is fine in most cases, it does not quite serve our use case for 
> metrics. 
> So we need to decide how are we going to encode and decode metric values and 
> store them in HBase.
>  



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